Electric circuit breaker



C. THUMIM May 194 2.

ELECTRIC CIRCUIT BREAKER I '2 Sheets-Sheet 1 Filed May 2, 1940 G.-- MD Inventor": Carl Thumim,

by C. H is Attorney C. THUMIM ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed May 2, 1940 Inventor:

Car l Thumim jfa/myflm a Hls Attomey. r

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Patented May 19, 1942 UNITED ,STATES PATENT OFFICE ELECTRIC CIRCUIT BREAKER Carl Thumim, Yeadon, Pa., assignor to General j Electric Company, a corporation of New York Application May 2, 1940, Serial No. 332,960" 8 Claims. (01.200-163) My invention relates to electric circuit breakers and more particularly to the contact structure of electric circuit breakers.

Circuit breakers employing reciprocating conducting members have been used heretofore. In

order to make electrical connection with the re-' ciprocating conducting member, sliding contacts have been provided which have assumed various However, difiiculties have been encountered when using the sliding contacts of the prior art in conjunction with high-speed circuit breakers for interrupting circuits carrying large amounts of power, for example, such as the circuit breaker disclosed and claimed in the Prince et a1. copending application Serial No. 303,126, filed November 6, 1939, and assigned to the as signee of the present application.

A rapidly moving reciprocating conducting member, such as the reversing blade disclosed in the above-mentioned copending application, causes chattering of the contact fingers associated with the sliding contact and consequent burning due to the arcing. Furthermore, when the contact fingers of the prior-art arrangements are arranged to eliminate arcing for one direction of movement of the reciprocating contact blade, chattering and resultant arcing will occur when the reverse blade movement takes place. It would be desirable, therefore, to provide a sliding contact structure which would eliminate destructive arcing which occurs when the sliding contacts of the prior .art are used with highspeed circuit breakers for interrupting large amounts of power.

It is an object of my invention, therefore, to provide a new and improved contact structure which will eliminate the difiiculties encountere with arrangements used heretofore.

It is another object of my invention to provide 'a sliding contact structure for use with a reciprocally movable conducting member wherein chattering and consequent burning of the conducting member is completely eliminated for either direction of movement thereof.

It is another object of my invention to provide a sliding contact structure for circuit breakers wherein the contact fingers are provided with biasing means characterized by different periods of vibration.

Further objects and advantages of my inven- For a better understanding of my invention, reference maybe had to the accompanying drawings in which Fig. 1 is a schematic diagram partly in sectionof a circuit breaker employing the sliding contact structure of my invention, Fig. 2 is an enlarged View partly in section of the sliding contact structure shown in Fig. 1, Fig. 3 is a top View partly in section of the contact structure of Fig. 2, Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 2, Fig. 5 is a perspective view of the contact fingers used in conjunction with my invention, and Fig. 6 is a detailed view partly in section of a portion of the contact fingers of Fig. 5 to illustrate the details in construction thereof.

Although my. invention is of general application for use with circuit breakers requiring a sliding contact, I have illustrated my invention in Fig. 1 as applied to a circuit breaker ll] of the cross gas-blast type disclosed and claimed in the above-mentioned Prince et al. application. Circuit breaker IO comprises a stationary contact V tor, 20 located within insulator I6.

II and a movable contact I2 arranged to be operated so as to draw an arc in arc chute l3. The stationary or fixed contact II is connected to a conducting member I4 which, in turn, is associated with a line terminal, not shown. Movable contact I2 is arranged to reciprocate for opening and closing the circuit associated with circuit breaker In so as to make sliding contact with the contact structure embodying my inventionand generally indicated at I5. Contact structure I5 is arranged to be connected to a line terminal, not shown, through a conductor housed within insulating member l6. Immediately after the separation of contacts [I and I2, the arc drawn therebetween is driven by an air or gas blast from conduit l1 into arc chute l3 against a plurality of partitions l8, which .partitions are transverse to the arc gap and the ends of which extend close to the path of movement of reciprocating or reversible blade I2.

Referring now to Figs. 2, 3, and 4, wherein the sliding contact structure of my invention is illustrated in detail, I- have shown a support or housing I91electrically connected to a lead-in conduc- I-Iousing l9 includes two hollow squares I9a and I9'b located adjacent to one another but separated sufficienttion will becomeapparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and, forming apart of this specification.

1y to define an opening 2| through which reciprocating o-r reversible blade I2 is adapted to move. A closure plate 22 (Figs. 2 and 3) is provided to close the opening between hollow squares [9a and I9b at the ends thereof remote from insulator I6 and, therefore, further define opening;

2|. Hollow squares [9a and l9b are also provided with integral extensions 23a, 24a, and 23b, 24b, respectively. Extensions 23a and 23b are provided with cooperating openings for supporting pin 25 upon which roller 26 is rotatably mounted. Similarly, extensions 24a and 24b are provided with cooperating openings for supporting pin 21 upon which roller 28 is rotatably mounted. Rollers 26 and 28 are provided to guide reciprocating conducting member 12 in its movement through the opening 2| in housing l9.

The housing I9 is completed by conducting cover plates 29a and 29b engaging with the edges of hollow squares la and l9b, respectively, to which they are fastened by suitable fastening means 30a and 3%, respectively. In order to insure good electrical connections between conducting cover plates 29a and 29b with hollow squares [9a and lSb, I provide raised contact surfaces 3| on the cooperating surfaces of cover plates 29a and 29b, which may be silver-line contacts of the type described and claimed in the copending application of Weder et al., Serial No. 314,826, filed January 20, 1940, and assigned to the assignee of the present application.

The sliding contacts of the prior art usually included a plurality of contact fingers for engaging the movable conducting member. I have found that, if these fingers extend in only one of the directions of movement of the reciprocating conducting member, chattering and consequent burning of the parts of the sliding contact occur during movement of the conducting member in the opposite direction. Accordingly, in order to remove this diificulty and to provide good electrical contact between conducting plates 29a and 29b and reciprocating blade I2, I provide a plurality of pairs of identical contact fingers 32 and 33 milled in the center so as to nest together loosely in a scissorslike or X fashion as best shown in Fig. 5. Sets of these conducting fingers 32 and 33 arranged in X fashion are mounted within each hollow square lQa and H519, as best shown in Fig. 4. Since the conducting contact fingers arranged in X or scissorslike fashion mounted within hollow square lQa are identical with those mounted within hollow square llb, only the description of the former will be included hereinafter. One end of each of the contact fingers 32 and 33 arranged in scissors or X fashion engages with one side of reciprocating conducting member 12 while the other ends thereof engage with conducting plate 29a.

In order to bias contact fingers 32 and 33 into current-conducting relationship between reciprocating conducting member l2 and conducting cover plates 29a and 291), I provide resilient means including springs 34 and 35 of different sizes, as shown in Figs. 2, 3, and 6 and described in greater detail hereinafter. As shown in Fig. 6, the ends of each of the contact fingers 32 and 33 are provided with a relatively large diameter shallow recess 36 for accommodating the ends of large springs 34 and a somewhat deeper recess 3"! of smaller diameter for accommodating the ends of smaller springs 35. The rapidly moving reciprocating conducting member II! has a tendency to set up vibrations of the sets of contact fingers 32 and 33 and, if all these fingers vibrated in unison, arcing would result tending to pit and destroy the conducting members. For this reason, springs 34 and 35 of different sizes are associated with different sets of conducting fingers arranged in scissorslike fashion so as to vary the force applied on the difierent pairs of fingers and to cause different natural periods of vibration, whereby vibration in unison of all the fingers is prevented and contact of some of the fingers, regardless of the disturbing effect of the rapidly moving reversible blade, is assured at all times. By using two different spring sizes 34 and 35, sets of contact fingers having three different natural periods of vibration may be provided since these fingers may be arranged so that certain pairs use only large springs 34, others use only small springs 35, and still others use a combination of both springs 34 and 35 as shown in Figs. 2 and 6.

Although I have illustrated the resilient means including springs 34 and 35 as of the compression type located between the ends of fingers 32 and 33 arranged in scissorslike or X fashion, it will be understood by those skilled in the art that tension springs could be provided to perform the same function. The number of pairs of contact fingers 32 and 33 arranged on either side of reciprocating conducting blade l2 will depend upon the current to be carried by sliding contact l5 and, by way of example in Fig. 2, I have shown an arrangement employing five pairs of conducting fingers 32 and 33 arranged in scissorslike or X fashion engaging with each side of reciprocating conducting member l2. It will be observed that conducting fingers 32 and 33 are identical and may be constructed by being sliced off to the proper thickness from long lengths of material after which the centers thereof are milled for proper nesting and the ends thereof are counterbored to accommodate the various spring combinations. In order that the contact fingers 32 and 33 arranged in scissors fashion may be held in position in housing 19 for assembly purposes, rods 38, one supported by each of the hollow squares lQa and l9b, are provided. Also, in order to lubricate the sliding contact l5 and prevent extraneous dirt from entering housing I9, I provide wipers 39 supported by housing l9 adjacent the edges of opening 21, which may comprise pieces of felt saturated with lubricating oil.

From the above discussion, it will be observed that, for either direction of movement of reciprocal conducting member I2, a plurality of contact fingers are provided substantially extending in one of these directions of movement while a cooperating group of fingers are provided extending in the other direction of movement. Although the contact fingers 32 and 33 are not arranged parallel with conducting member l2, one of these fingers makes an acute angle with conducting member [2 with reference to one direction of movement thereof whereas the other contact finger makes an acute angle with conducting member l2 with reference to the other direction of movement. Therefore, for either direction of movement of the reciprocating member l2, only one group of fingers, for example 32, will tend to chatter while the other group of fingers, for example 33, will tend to make good contact therewith, and the difficulties encountered in connection with sliding contacts of the prior art where the contact fingers extend in only one direction have been eliminated.

While I have shown and described a particular embodiment of my invention as applied to a sliding contact for electric circuit breakers, I do not desire my invention to be limited to the construction shown and described for it Will, of course, be obvious to those skilled in the art that changes and modifications may be made conducting relationship, means interposed between said members for insuring continuous electrical connection therebetween comprising a pair of contacts arranged in a scissorslikemanner having certain ends thereof biased into cur-.

rent-carrying engagement with one of said reladucting members, one of which is arranged for interposed between said members for insuring electrical'current conduction therebetween comtively. movable members, while the other ends thereof are biased into sliding engagementwith the other of said relatively movable members.

2. In a sliding contact for an electric circuit interrupter, a pair of conducting members arranged continuously to be in conducting relationship; one of which is arranged for reciprocal movement relative to the other, means interposed between said members comprising. a pair of contacts arranged at an angle with respect to each other and with said conducting members, one of said contacts making an acute angle with said reciprocating member'with reference to one direction of movement thereof, while said other contact makes an acute angle with said reciprocating member with reference to the other direction of movement thereof so as to insure continuous electrical connection between said members regardless of the direction of movement of said one member or the speed with which it moves.

3. A sliding contact for an electric circuit breaker having a reciprocating conducting member and a stationary support associated therewith comprising means interposed between said support and said conducting member for insuring electrical current conduction therebetween including a plurality of fingerlike contacts, pairs of which are arranged in a scissorslike manner, resilient means for each of said pairs of contacts for biasing said contacts into engagement with both said support and said conducting member, said resilient means for said different pairsof contacts being characterized by different natural periods of vibration. r

4. In an electric circuit breaker, a pair of conducting members, one of which is arranged for reciprocal movementrelative to the other, means interposed between said member for insuring electrical current conduction therebetween comprising a pair of fingerlike contacts, each having the central portion thereof recessed so as to,

nest together in scissorslike fashion, and resilitact for biasing them into continuous currentconducting engagement withsaid conducting members.

5. In an electric circuit breaker, a pair of conprising a plurality of pairs of fingerlike contacts arranged in X fashion, spring means associated with each of said pairs of fingerlike contacts and supported in recesses adjacent the ends thereof, said spring means for said different pairs of contacts being constructed so as to provide different natural periods of vibration for different ones of said pair of contacts.

6. In an electric circuit breaker, a housing including a pair of conducting plates, said housing being constructed to define an opening therethrough parallel with said conducting plates and midway therebetween, a conducting member arranged for reciprocal movement in said opening, means contained in said housing and interposed between said plates and said reciprocating conducting member for providing a continuous current-conducting path therebetween comprising a plurality of pair of fingerlike contacts arranged in X fashion, resilient means for biasing said pairs of contacts into engagement with said reciprocating conducting member and said plates, said resilient means for different pairs of said contacts being characterized by different natural periods of vibration.

7. In an electric circuit breaker, a pair of conducting members, one of which is arranged for reciprocal movement relative to the other, means interposed between said members for insuring continuous electrical current conduction therebetween comprising a pair of fingerlike contacts arranged in X fashion, a portion of the ends of said fingerlike contacts being cut away to provide a recess having a plurality of different areas of cross section to accommodate one or more springs of different sizes for biasing said contacts into engagement with both of said conducting members.

8. In an electric circuit breaker, a housing including a pair of conducting plates, said housing being constructed to define an opening therethrough parallel with said conducting plates and midway therebetween, a conducting member arranged for reciprocal movement in said opening, a plurality of rollers supported by said housing for guiding said conducting member through said opening, means contained in said housing and interposed between said plates and said reciprocating conducting member for providing a I ent means associated withsaid fingerlike concontinuous current-conducting path therebetween comprising a plurality of pairs of fingerlike contacts arranged in -X fashion, resilient, 1 means for biasing said pairs of contacts into engagement with said reciprocating conducting member and said plates, said resilient means for different pairs of said contacts being characterized by different natural periods of vibration.

CARL THUMIM. 

